transmogrify: Add support for NDSize -> PyObject *

Support downgrading of types if all values inside the NDSize
are smaller then max(long)
PyDataArray: Add data_extent property (getter)

Returns a n-tuple where n is the dimensionality of the data and
the the individual elements the size of each dimension
test: Add test for PyDataArray::data_extent property
transmogrify: Add support for PyObject* -> NDSize
PyDataArray: Add data_extent property (setter)
test: Add test for setting PyDataArray::data_extent
Merge pull request #20 from gicmo/data_extent

Add support for DataArray::dataExtent

Verry nice